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We know that a noncommutative vector bundle is a finitely generated projective $A$-module where $A$ is a non commutative $C^{*}$ algebra. In this question we introduce a particular non commutative $C^{*}$ algebra $A$ and a particular $A$- bimodule $M$, see Construction below. Then our question would be :

Is this particular $M$ a finitely generated projective $A$-module ?

If the answer is yes, how can we compute non commutative characteristic classes of such non commutative vector bundle?

Construction:

Let $N$ be a compact smooth Riemannian manifold. By $\lambda^{p}(N)$ we mean the space of all smooth complex valued $(0,p)$ tensors on $M$. Our pre $C^{*}$ algebra is $A=\lambda^{*}(N)=\oplus \lambda^{p}(N)$ which multiplication is the tensor product. We can equip $A$ to a pre-$C^{*}$ algebra structure as follows: If $\alpha \in \lambda^{p}(N)$, we define $\parallel \alpha \parallel= \sup \parallel \alpha_{x}\parallel ,\;\;x\in N$. The later norm is the standard "multilinear norm" for $p$-linear maps on the tangent space $T_{x} N$.Then we take the sup-norm to define a norm on $\lambda^{*}(N)$ as a graded algebra. (Note that when we restrict $A$ and $M$ to $T_{x} N$, that is we consider a linear problem, we obtain an $AF$ algebra,"http://en.wikipedia.org/wiki/Approximately_finite-dimensional_C*-algebra". What is the K groups of this $AF$ algebra?)

Our module $M$ is $M=\Omega^{*}(N)$, the space of differential forms. Now we define the scalar product as follows:

In a local coordinate $\lambda \in A$ and $\alpha \in M$ are a sum of the following objects:

$\lambda=dx_{i_{1}}\otimes \ldots \otimes dx_{i{k}}\;\;\; \alpha=dx_{j_{1}} \wedge \ldots \wedge dx_{j_{l}}$ we define $\lambda.\alpha=dx_{i_{1}}\wedge \ldots \wedge dx_{i{k}} \wedge dx_{j_{1}} \wedge \ldots \wedge dx_{j_{l}}$

This is independent of choosing a particular local coordinate.

Are there some geometric or topological information of M in the cohomology of $A$ with coefficient in $M$?

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  • $\begingroup$ So, is the question as follows: Is any module over a noncommutative $C^*$ algebra a finitely generated projective module over the noncommutative $C^*$ algebra? $\endgroup$
    – user62675
    Commented May 10, 2014 at 21:38
  • $\begingroup$ @SanathDevalapurkar My question is not this. I do not underestand why you think this is equivalent to my question?could you please more explain? $\endgroup$ Commented May 14, 2014 at 19:24
  • $\begingroup$ You asked «Is M a finitely generated projective A-module?» but you did not impose any conditions on the module... Are you asking how can one recognize a f.g. projective module or what, exactly? $\endgroup$ Commented May 14, 2014 at 20:12
  • $\begingroup$ What follows the subtitle «construction» does not have any obvious connection with what precedes it... $\endgroup$ Commented May 14, 2014 at 20:13
  • $\begingroup$ @MarianoSuárez-Alvarez I add a few words to my question. Now is it clear? $\endgroup$ Commented May 14, 2014 at 20:37

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